The main parachute lid release mechanism worked and the first main parachute also inflated well, but several radial tears in the fabric were observed immediately following extraction from the main parachute bag, before the parachute experienced maximum load.

The second pyrotechnic mortar also worked normally, ejecting the second pilot chute, which also inflated as expected. The second main parachute was extracted from its bag, but one radial tear was observed, again before reaching peak inflation loads.

Why the Exomars EDL system needs four separate parachutes when MSL/M2020 only needs one I don't know.

To oversimplify, parachute failures come in two flavors: the parachute fabric tears (sometimes catastrophically), or the parachute fails to inflate ("squidding"). I seem to recall both types of failure in MSL testing, but I don't recall for sure at the moment.

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Disclaimer: This post is based on public information only. Any opinions are my own.

I think the complexity comes from the fact that neither ESA nor RSA have flown a successful very large Martian 'chute before, so I can understand the desire to 'stage' them with something small and tough, followed by something larger that doesn't have to be strong enough to handle the supersonic deployment. The LDSD deployment used that balute first as a drogue, to then pull out the main (but had two failures of the mains)

I'm at a loss as to how they got to the Drogue-1st Stage Main-Drogue 2-2nd Stage Main four chute design. I'm sure they're not doing it for fun.

The ExoMars EDM had a Disk-Gap-Band canopy of 12m.....but they're not re-using that flight proven design at all (it would make sense as a 1st Stage Main chute - instead they've developed a new 15m chute)

The final Rover EDL chute is for some reason, 35m across. That's more than 50% larger than the MSL 19.7m parachute despite being a lighter entry vehicle.

This was a concern I had about the EDM being so close to the rover mission....there simply isn't the time to take the lessons learned from EDM and then apply those to the design of the rover EDL.

There was an excellent documentary on the MER project which followed Steve Squyres as the mission developed. I forget its name now. But I recall him saying parachutes were a 'black art' or words to that effect, not really understood as well as you would expect. The inflation process must be a bit chaotic.

...I do hope that ESA consults JPL for their decades of experience in this black art.

As I mentioned upthread, even if there weren't export controls it's unclear if ESA would ask or JPL would respond in detail if they did.

There's a certain amount of open-literature info about US Mars parachute development from Viking on. All the failures on LDSD indicate that there are limits to our knowledge on this, though all the ASPIRE testing makes one feel pretty confident in the MSL parachute design.

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Disclaimer: This post is based on public information only. Any opinions are my own.

I'm at a loss as to how they got to the Drogue-1st Stage Main-Drogue 2-2nd Stage Main four chute design. I'm sure they're not doing it for fun.

I had the same reaction - in a comment at IPPW I described this design as 'baroque'. Introducing an extra serial step introduces another failure point - the tradeoff presumably being the ability to nudge all of the elements in the chain further from operating environments (Mach, q, Re etc.) in which they are known to fail.....

Maybe there are lower descent speed requirements on their landing site acquisition?

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Space Enthusiast Richard Hendricks --"The engineers, as usual, made a tremendous fuss. Again as usual, they did the job in half the time they had dismissed as being absolutely impossible." --Rescue Party, Arthur C ClarkeMother Nature is the final inspector of all quality.

Thanks for the link to the ESA page : I discovered this EDL procedure which seems quite 'baroque' to me also, with all those parachutes sequences embedded in one another.Many failure points are at risk and I would have liked Jim Martin (Viking Program Manager) to give us his opinion on the subject.Then... let's go back to the basics ...which are still to be considered as a technological feat even 43 years after the successful landings of the two Viking spacecrafts !

This reminds me of the fluid dynamics issues that complicated the Wright Brothers' development of the first propellers used in HTA aviation. "We had thought we could adopt the theory from marine engineers, and then by using our tables of air pressures, instead of the tables of water pressures used in their calculations, that we could estimate in advance the performance of the propellers we could use." That proved to be incorrect, and they had to begin with no useful specific from marine propellers. "It is hard to find even a point from which to make a start; for nothing about a propeller, or the medium in which it acts, stands still for a moment." They ended up testing 200 different wing designs in wind tunnels and then used what they learned about wings to design their propellers.

Fluid dynamics is not good old Newtonian predictable physics.

I have leapt out of a plane once, and one of the things they taught me during training was how to perform a little maneuver that decreases the probability that the chute fails to open, something that can occur if it unfortunately inhabits a small wind-less pocket behind the parachutist's back and never catches the winds that open it. (The aforementioned physical maneuver and a backup parachute are hedges against that possibility.)

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